They're a great companion book, but you really need a book that guides you through derivations and computations. Some techniques are non-obvious like choosing c

They're a great companion book, but you really need a book that guides you through derivations and computations. Some techniques are non-obvious like choosing coordinate systems to make integrals easier, clever contours when applying residue theorem, change of variables using orthogonal matrices to diagonalize symmetric matrices, etc.